Tue·Aug 8, 2017Tuesday·August 8, 2017

1. 01*

   Probing the Sea Quark Content of the Proton with One-Particle-Inclusive Processes

   Ignacio Borsa🇦🇷 · Rodolfo Sassot🇦🇷 · Marco Stratmann🇩🇪

   We investigate the feasibility of constraining parton distribution functions in the proton through a comparison with data on semi-inclusive deep-inelastic lepton-nucleon scattering. Specifically, we reweight replicas of these distributions according to how well they reproduce recent, very precise charged kaon multiplicity measurements and analyze how this procedure optimizes the determination of the sea quark densities and improves their uncertainties. The results can help to shed new light on the long standing question on the size of the flavor and charge symmetry breaking among quarks of radiative origin. An iterative method is proposed and adopted to account for the inevitable correlation with what is assumed about the parton-to-hadron fragmentation functions in the reweighting procedure. It is shown how the fragmentation functions can be optimized simultaneously in each step of the iteration. As a first case study, we implement this method to analyze kaon production data.

   hep-phhep-exPRD(2017)·36 citations
2. 02*

   Possible Beyond the Standard Model Physics Motivated by Muonic Puzzles

   Yu-Sheng Liu🇺🇸

   Recent measurements of the proton radius using the Lamb shift in muonic hydrogen are troublingly discrepant with values extracted from hydrogen spectroscopy and electron-proton scattering experiments. This discrepancy, which differs by more than five standard deviations, may be a signal of new physics caused by a violation of lepton universality. Another candidate for a new physics signal is the muon anomalous magnetic moment. The measurement at BNL differs from the standard model prediction by at least three standard deviations. Motivated by these two puzzles, first we use polarized lepton-nucleon elastic scattering to search for a new scalar boson, and furthermore we suggest new measurements of the nucleon form factors. Next, we display a method to analyze the beam dump experiments without using approximation on phase space, and we use it to constrain all possible new spin-0 and spin-1 particles, and a variety of other measurements to study the possibility of the new physics. Finally, assuming a new scalar boson can solve the two puzzles simultaneously, we present a general model-independent analysis and constrain the existence of the new physics.

   hep-phhep-exnucl-thphysics.atom-ph2 citations
3. 03*

   Helicity Antenna Showers for Hadron Colliders

   Nadine Fischer🇦🇺 · Andrew Lifson🇦🇺 · Peter Skands🇦🇺

   We present a complete set of helicity-dependent 2->3 antenna functions for QCD initial- and final- state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2->2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226.

   hep-phEPJC(2017)·20 citations
4. 04*

   Glauber Gluon Effects in Soft Collinear Factorization

   Gao-Liang Zhou🇨🇳 · Zheng-Xin Yan🇨🇳 · Xin Zhang🇨🇳 · Feng Li🇨🇳

   Effects of Glauber gluons, which cause the elastic scattering process between different jets, are studied in the frame of soft-collinear effective theory(SCET). Glauber modes are added into the Lagrangian before integrated out, which is helpful in studies on Glauber couplings of collinear and soft particles explicitly. It is proved that interactions after the hard collision cancel out in processes inclusive enough. So are interactions with the light cone coordinates Sx^{+}$and$x^{-}$ greater than those of the hard collision. Eikonalization of Glauber couplings of active particles and absorption of active-active and active-soft and active-spectator Glauber exchanges into soft and collinear Wilson lines are discussed, which is related to loop level definitions of Glauber gluons here. The active-spectator coherence are proved to be harmless on inclusive summation of spectator-spectator and spectator-soft Glauber exchanges. Based on this result, spectator-spectator and spectator-soft Glauber exchanges are proved to cancel out in processes considered here. Graphic aspects of the cancellation are also discussed to explain relations between the graphic cancellation of Glauber gluons in the frame of perturbative QCD and operator level skills in the paper.

   hep-ph1 citation
5. 05*

   Supersymmetric Extension of Preonic Models: General Remarks

   B. B. Oner🇹🇷 · S. Sultansoy🇹🇷

   We present some general remarks on supersymmetric extensions of fermion-scalar and three-fermion preonic models with an assumption of supersymmetry is realized at preonic level. The motivation and the requirement of this assumption are briefly given. In general, supersymmetric extensions of fermion-scalar (three-fermion) models predict 4 (10) "super" partners for each Standard Model fermion.

   hep-ph0 citations
6. 06*

   What measurements of neutrino neutral current events can reveal

   Raj Gandhi🇮🇳 · Boris Kayser🇺🇸 · Suprabh Prakash🇧🇷 · Samiran Roy🇮🇳

   We show that neutral current (NC) measurements at neutrino detectors can play a valuable role in the search for new physics. Such measurements have certain intrinsic features and advantages that can fruitfully be combined with the usual well-studied charged lepton detection channels in order to probe the presence of new interactions or new light states. In addition to the fact that NC events are immune to uncertainties in standard model neutrino mixing and mass parameters, they can have small matter effects and superior rates since all three flavours participate. We also show, as a general feature, that NC measurements provide access to different combinations of CP phases and mixing parameters compared to CC measurements at both long and short baseline experiments. Using the Deep Underground Neutrino Experiment (DUNE) as an illustrative setting, we demonstrate the capability of NC measurements to break degeneracies arising in CC measurements, allowing us, in principle, to distinguish between new physics that violates three flavour unitarity and that which does not. Finally, we show that NC measurements can enable us to restrict new physics parameters that are not easily constrained by CC measurements.

   hep-phJHEP(2017)·19 citations
7. 07*

   Quasi-two-body decays $B_{(s)}\to D(\rho (1450),\rho (1700))\to D\pi \pi$ in the perturbative QCD factorization approach

   Ai-Jun Ma🇨🇳 · Ya Li🇨🇳 · Wen-Fei Wang🇨🇳 · Zhen-Jun Xiao🇨🇳

   By employing a framework for the quasi-two-body decays in the perturbative QCD (PQCD) factorization approach, we calculate the branching ratios of the decays $B_{(s)}\to D(\rho (1450),\rho (1700))\to D\pi \pi$ with $D=(D_{(s)},{\bar{D}}_{(s)})$. The pion vector form factor $F_{\pi }$, acquired from a {\it BABAR} Collaboration analysis of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}(\gamma )$ data, is involved in the two-pion distribution amplitudes ${\Phi }_{\pi \pi }^{I=1}$. The PQCD predictions for the branching ratios of the considered quasi-two-body decays are in the range of $10^{-10}\sim 10^{-4}$. The PQCD predictions for $\mathcal{B}(B^0\to {\bar{D}}^0({\rho }^0(1450),{\rho }^0(1700))\to {\bar{D}}^0{\pi }^{+}{\pi }^{-})$ agree well with the measured values as reported by LHCb if one takes still large theoretical errors into account. Unlike the traditional way of the PQCD approach, one can extract the decay rates for the two-body decays $B_{(s)}\to D(\rho (1450),\rho (1700))$ from the results of the corresponding quasi-two-body decays. The PQCD predictions for $\mathcal{B}(B_{(s)}\to D\rho (1450))$ and $\mathcal{B}(B_{(s)}\to D\rho (770))$ are similar in magnitude: an interesting relation to be tested by future experimental measurements.

   hep-phPRD(2017)·31 citations
8. 08*

   Interference effect as resonance killer of newly observed charmoniumlike states $Y(4320)$ and $Y(4390)$

   Dian-Yong Chen🇨🇳 · Xiang Liu🇨🇳 · Takayuki Matsuki🇯🇵

   In this letter, we decode the newly observed charmoniumlike states, $Y(4320)$ and $Y(4390)$, by introducing interference effect between $\psi (4160)$ and $\psi (4415)$, which plays a role of resonance killer for $Y(4320)$ and $Y(4390)$. It means that two newly reported charmoniumlike states are not genuine resonances, according to which we can naturally explain why two well-established charmonia $\psi (4160)$ and $\psi (4415)$ are missing in the cross sections of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$ and ${\pi }^{+}{\pi }^{-}{h}_c$ simultaneously. To well describe the detailed data of these cross sections around $\sqrt{s}=4.2$ GeV, our study further illustrates that a charmoniumlike structure $Y(4220)$ must be introduced. As a charmonium, $Y(4220)$ should dominantly decay into its open-charm channel $e^{+}{e}^{-}\to D^0{\pi }^{+}{D}^{\ast -}$, which provides an extra support to $\psi (4S)$ assignment to $Y(4220)$. In fact, this interference effect introduced to explain $Y(4320)$ and $Y(4390)$ gives a typical example of non-resonant explanations to the observed $XYZ$ states, which should be paid more attention especially before identifying the observed $XYZ$ states as genuine resonances.

   hep-phhep-exEPJC(2018)·31 citations
9. 09*

   Formation and Deformation of the $\psi (3770)$

   Susana Coito🇵🇱 · Francesco Giacosa🇩🇪

   The form of resonance line-shapes unveils information about its nonperturbative properties and formation mechanisms. Here, we study the non-Breit-Wigner energy distribution of the resonance $\psi (3770)$ using an unitarized effective Lagrangian approach, that includes the effect of the nearby threshold $D^{+}{D}^{-}$. Two poles are found in the second Riemann sheet near the resonance amplitude. We discuss the setting of the free parameters and possible effects contributing to the signal.

   hep-phActa Phys.Polon.Supp.(2017)·3 citations
10. 10*

    CP Violation in Multibody $B$ Decays from QCD Factorization

    Rebecca Klein🇩🇪 · Thomas Mannel🇩🇪 · Javier Virto🇩🇪 · K. Keri Vos🇩🇪

    We test a data-driven approach based on QCD factorization for charmless three-body $B$-decays by confronting it to measurements of CP violation in $B^{-}\to {\pi }^{-}{\pi }^{+}{\pi }^{-}$. While some of the needed non-perturbative objects can be directly extracted from data, some others can, so far, only be modelled. Although this approach is currently model dependent, we comment on the perspectives to reduce this model dependence. While our model naturally accommodates the gross features of the Dalitz distribution, it cannot quantitatively explain the details seen in the current experimental data on local CP asymmetries. We comment on possible refinements of our simple model and conclude by briefly discussing a possible extension of the model to large invariant masses, where large local CP asymmetries have been measured.

    hep-phhep-exJHEP(2017)·67 citations
11. 11*

    Importance of initial and final state effects for azimuthal correlations in p+Pb collisions

    Moritz Greif🇩🇪 · Carsten Greiner🇩🇪 · Björn Schenke🇺🇸 · Sören Schlichting🇺🇸 · Zhe Xu🇨🇳

    We investigate the relative importance of initial and final state effects on azimuthal correlations of gluons in low and high multiplicity p+Pb collisions. To achieve this, we couple Yang-Mills dynamics of pre-equilibrium gluon fields (IP-GLASMA) to a perturbative QCD based parton cascade for the final state evolution (BAMPS) on an event-by-event basis. We find that signatures of both the initial state correlations and final state interactions are seen in azimuthal correlation observables, such as $v_2\left\{2PC\right\}(p_T)$, their strength depending on the event multiplicity and transverse momentum. Initial state correlations dominate $v_2\left\{2PC\right\}(p_T)$ in low multiplicity events for transverse momenta $p_T>2\mathrm{GeV}$. While final state interactions are dominant in high multiplicity events, initial state correlations affect $v_2\left\{2PC\right\}(p_T)$ for $p_T>2\mathrm{GeV}$ as well as the pT integrated $v_2\left\{2PC\right\}$.

    hep-phnucl-thPRD(2017)·84 citations
12. 12*

    String-Inspired Special Grand Unification

    Naoki Yamatsu🇯🇵

    We discuss a grand unified theory (GUT) based on an $SO(32)$ GUT gauge group broken to its subgroups including a special subgroup. In the $SO(32)$ GUT on six-dimensional (6D) orbifold space $M^4\times T^2/{\mathbb{Z}}_2$, one generation of the SM fermions can be embedded into a 6D bulk Weyl fermion in the $SO(32)$ vector representation. We show that for a three generation model, all the 6D and 4D gauge anomalies in the bulk and on the fixed points are canceled out without exotic chiral fermions at low energies.

    hep-phhep-thPTEP(2017)·12 citations
13. 13*

    Stellar Recipes for Axion Hunters

    Maurizio Giannotti🇺🇸 · Igor G. Irastorza🇪🇸 · Javier Redondo🇪🇸 · Andreas Ringwald🇩🇪 · Ken'ichi Saikawa🇩🇪

    There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu--Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -- the hypothetical pseudo Nambu--Goldstone boson predicted by the Peccei--Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -- the fifth force experiment ARIADNE and the helioscope IAXO -- can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter.

    hep-phastro-ph.HEastro-ph.SRJCAP(2017)·258 citations
14. 14*

    Electroweak Vacuum Collapse induced by Vacuum Fluctuations of the Higgs Field around Evaporating Black Holes

    Kazunori Kohri🇯🇵 · Hiroki Matsui🇯🇵

    In this paper, we discuss the Higgs vacuum stability around evaporating black holes. We provide a new approach to investigate the false vacuum decay around the black hole and clearly show how vacuum fluctuations of the Higgs induce a gravitational collapse of the vacuum. Furthermore, we point out that the backreaction of the Hawking radiation can not be ignored and the gravitational vacuum decay is exponentially suppressed. However, a large number of the evaporating (or evaporated) primordial black holes threaten the existence of the Universe and we obtain a new upper bound on the evaporating PBH abundance from the vacuum stability. Finally, we show that the high-order corrections of the BSM or QG would not destabilize the Higgs potential, otherwise even a single evaporating black hole triggers a collapse of the electroweak vacuum.

    hep-phastro-ph.COgr-qchep-thPRD(2018)·61 citations
15. 15*

    8th CERN - Latin-American School of High-Energy Physics

    M. Mulders🇨🇭 · G. Zanderighi🇨🇭

    The CERN-Latin-American School of High-Energy Physics is intended to give young physicists an introduction to the theoretical aspects of recent advances in elementary particle physics. These proceedings contain lecture notes on the Standard Model of electroweak interactions, flavour physics, neutrino physics, Higgs physics, new physics beyond the standard model, quantum chromodynamics under extreme conditions, cosmology, an introduction to experimental facilities at the high-energy frontier, and practical statistics for particle physicists.

    hep-ph5 citations
16. 16*

    Cobimaximal Neutrino Mixing from $A_4$ and its Possible Deviation

    Ernest Ma🇺🇸 · G. Rajasekaran🇮🇳

    It has recently been shown that the phenomenologically successful pattern of cobimaximal neutrino mixing (${\theta }_{13}\ne 0$, ${\theta }_{23}=\pi /4$, and ${\delta }_{CP}=\pm \pi /2$) may be achieved in the context of the non-Abelian discrete symmetry $A_4$, if the neutrino mass matrix is diagonalized by an orthogonal matrix $\mathcal{O}$. We study how this pattern would deviate if $\mathcal{O}$ is replaced by an unitary matrix.

    hep-phEPL(2017)·29 citations
17. 17*

    Tracking down Quirks at the Large Hadron Collider

    Simon Knapen🇺🇸 · Hou Keong Lou🇺🇸 · Michele Papucci🇺🇸 · Jack Setford🇬🇧

    Non-helical tracks are the smoking gun signature of charged and/or colored quirks, which are pairs of particles bound by a new, long-range confining force. We propose a method to efficiently search for these non-helical tracks at the LHC, without the need to fit their trajectories. We show that the hits corresponding to quirky trajectories can be selected efficiently by searching for co-planar hits in the inner layers of the ATLAS and CMS trackers, even in the presence of on average 50 pile-up vertices. We further argue that backgrounds from photon conversions and unassociated pile-up hits can be removed almost entirely, while maintaining a signal reconstruction efficiency as high as 70%. With the 300 fb${}^{-1}$ dataset, this implies a discovery potential for string tension between 100 eV and 30 keV, and colored (electroweak charged) quirks as heavy as 1600 (650) GeV may be discovered.

    hep-phhep-exPRD(2017)·37 citations
18. 18*

    Improved limits for Higgs-portal dark matter from LHC searches

    Martin Hoferichter🇺🇸 · Philipp Klos🇩🇪 · Javier Menéndez🇯🇵 · Achim Schwenk🇩🇪

    Searches for invisible Higgs decays at the Large Hadron Collider constrain dark matter Higgs-portal models, where dark matter interacts with the Standard Model fields via the Higgs boson. While these searches complement dark matter direct-detection experiments, a comparison of the two limits depends on the coupling of the Higgs boson to the nucleons forming the direct-detection nuclear target, typically parameterized in a single quantity $f_N$. We evaluate $f_N$ using recent phenomenological and lattice-QCD calculations, and include for the first time the coupling of the Higgs boson to two nucleons via pion-exchange currents. We observe a partial cancellation for Higgs-portal models that makes the two-nucleon contribution anomalously small. Our results, summarized as $f_N=0.308(18)$, show that the uncertainty of the Higgs-nucleon coupling has been vastly overestimated in the past. The improved limits highlight that state-of-the-art nuclear physics input is key to fully exploiting experimental searches.

    hep-phastro-ph.COhep-exnucl-thPRL(2017)·127 citations
19. 19*

    Sterile Neutrinos and B-L Symmetry

    Pavel Fileviez Perez🇺🇸 · Clara Murgui🇪🇸

    We revisit the relation between the neutrino masses and the spontaneous breaking of the B-L gauge symmetry. We discuss the main scenarios for Dirac and Majorana neutrinos and point out two simple mechanisms for neutrino masses. In this context the neutrino masses can be generated either at tree level or at quantum level and one predicts the existence of very light sterile neutrinos with masses below the eV scale. The predictions for lepton number violating processes such as mu to e and mu to e gamma are discussed in detail. The impact from the cosmological constraints on the effective number of relativistic degree of freedom is investigated.

    hep-phastro-ph.COhep-exhep-thPLB(2018)·11 citations
20. 20*

    Solar neutrino flux at keV energies

    Edoardo Vitagliano🇩🇪 · Javier Redondo🇪🇸 · Georg Raffelt🇩🇪

    We calculate the solar neutrino and antineutrino flux in the keV energy range. The dominant thermal source processes are photoproduction ($\gamma e\to e\nu \bar{\nu }$), bremsstrahlung ($e+Ze\to Ze+e+\nu \bar{\nu }$), plasmon decay ($\gamma \to \nu \bar{\nu }$), and $\nu \bar{\nu }$ emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. These latter processes dominate in the energy range of a few keV and thus carry information about the solar metallicity. To calculate their rate we use libraries of monochromatic photon radiative opacities in analogy to a previous calculation of solar axion emission. Our overall flux spectrum and many details differ significantly from previous works. While this low-energy flux is not measurable with present-day technology, it could become a significant background for future direct searches for keV-mass sterile neutrino dark matter.

    hep-phastro-ph.SRJCAP(2017)·54 citations
21. 21*

    A cancellation mechanism for dark matter-nucleon interaction

    Christian Gross🇫🇮 · Oleg Lebedev🇫🇮 · Takashi Toma🇩🇪

    We consider a simple Higgs portal dark matter model, where the Standard Model is supplemented with a complex scalar whose imaginary part plays the role of WIMP dark matter (DM). We show that the direct DM detection cross section vanishes at tree level and zero momentum transfer due to a cancellation by virtue of a softly broken symmetry. This cancellation is operative for any mediator masses. As a result, our electroweak scale dark matter satisfies all of the phenomenological constraints quite naturally.

    hep-phPRL(2017)·161 citations
22. 22*

    Two-photon exchange correction to the hyperfine splitting in muonic hydrogen

    O. Tomalak🇩🇪

    We reevaluate the Zemach, recoil and polarizability corrections to the hyperfine splitting in muonic hydrogen expressing them through the low-energy proton structure constants and obtain the precise values of the Zemach radius and two-photon exchange (TPE) contribution. The uncertainty of TPE correction to S energy levels in muonic hydrogen of 105 ppm exceeds the ppm accuracy level of the forthcoming 1S hyperfine splitting measurements at PSI, J-PARC and RIKEN-RAL.

    hep-phnucl-exnucl-thphysics.atom-phEPJC(2017)·38 citations
23. 23*

    Hamilton-Jacobi formalism to warm inflationary scenario

    K. Sayar🇮🇷 · A. Mohammadi🇮🇷 · L. Akhtari🇮🇷 · Kh. Saaidi🇮🇷

    Hamilton-Jacobi formalism as a powerful method is being utilized to reconsider warm inflationary scenario, where the scalar field as the main component deriving inflation interacts with other field. Separating the context to strong and weak dissipative regimes, the goal is followed for two popular function of dissipation coefficient. Applying slow-rolling approximations, the required perturbation parameters are extracted and by comparison to the latest Planck data, the free parameters are restricted. Possibility of producing an acceptable inflation is studied where the result shows that for all cases the model could successfully suggests amplitude of scalar perturbation, scalar spectral index , its running, and the tensor-to-scalar ratio.

    ↳ gr-qchep-phPRD(2017)·46 citations
24. 24*

    Statistical nature of infrared dynamics on de Sitter background

    Junsei Tokuda🇯🇵 · Takahiro Tanaka🇯🇵

    In this study, we formulate a systematic way of deriving an effective equation of motion(EoM) for long wavelength modes of a massless scalar field with a general potential $V(\varphi )$ on de Sitter background, and investigate whether or not the effective EoM can be described as a classical stochastic process. Our formulation gives an extension of the usual stochastic formalism to including sub-leading secular growth coming from the nonlinearity of short wavelength modes. Applying our formalism to $\lambda {\varphi }^4$ theory, we explicitly derive an effective EoM which correctly recovers the next-to-leading secularly growing part at a late time, and show that this effective EoM can be seen as a classical stochastic process. Our extended stochastic formalism can describe all secularly growing terms which appear in all correlation functions with a specific operator ordering, which will not be a big drawback because the commutator of a light scalar field becomes negligible at large scales owing to the squeezing.

    ↳ gr-qchep-phhep-thJCAP(2018)·65 citations
25. 25*

    On the hydrodynamic attractor of Yang-Mills plasma

    Michał Spaliński🇵🇱

    There is mounting evidence suggesting that relativistic hydrodynamics becomes relevant for the physics of quark-gluon plasma as the result of nonhydrodynamic modes decaying to an attractor apparent even when the system is far from local equilibrium. Here we determine this attractor for Bjorken flow in N=4 supersymmetric Yang-Mills theory using Borel summation of the gradient expansion of the expectation value of the energy momentum tensor. By comparing the result to numerical simulations of the flow based on the AdS/CFT correspondence we show that it provides an accurate and unambiguous approximation of the hydrodynamic attractor in this system. This development has important implications for the formulation of effective theories of hydrodynamics.

    ↳ hep-thhep-phnucl-thPLB(2018)·106 citations
26. 26*

    Global inconsistency, 't Hooft anomaly, and level crossing in quantum mechanics

    Yuta Kikuchi🇯🇵 · Yuya Tanizaki🇺🇸

    An 't Hooft anomaly is the obstruction for gauging symmetries, and it constrains possible low-energy behaviors of quantum field theories by excluding trivial infrared theories. Global inconsistency condition is recently proposed as a milder condition but is expected to play an almost same role by comparing high symmetry points in the theory space. In order to clarify the consequence coming from this new condition, we discuss several quantum mechanical models with topological angles and explicitly compute their energy spectra. It turns out that the global inconsistency can be saturated not only by the ground-state degeneracy at either of high symmetry points but also by the level crossing (phase transition) separating those high symmetry points.

    ↳ hep-thcond-mat.str-elhep-phPTEP(2017)·85 citations
27. 27*

    Excitation energy spectra of the Lambda_c and Lambda_b baryons in a finite-size diquark model

    Kento Kumakawa🇯🇵 · Daisuke Jido (Tokyo Metropolitan University)🇯🇵

    The excitation energies of the ${\Lambda }_c$ and ${\Lambda }_b$ baryons are investigated in a finite-size diquark potential model, in which the heavy baryons are treated as bound states of a charm quark and a scalar-isoscalar diquark. The diquark is considered as a sizable object. The quark-diquark interaction is calculated as a sum of the quark-quark interaction which is assumed to be half of the quark-antiquark interaction for the color singlet. The potential parameters in the quark-antiquark interaction are fixed so as to reproduce the charmonium spectrum. We find the diquark size to be 1.1 fm for the diquark mass 0.5 GeV/c${}^2$ to reproduce the $1p$ excitation energy of ${\Lambda }_c$. In this model, the ${\Lambda }_c$ and ${\Lambda }_b$ excitation spectra are reproduced well, while this model does not explain ${\Lambda }_c(2765)$, whose isospin nor spin-parity are unknown yet. Thus, the detailed properties of ${\Lambda }_c(2765)$ is very important to the presence of the diquark in heavy baryons as a effective constituent. We also discuss the ${\Xi }_c$ spectrum with the scalar strange diquark.

    ↳ nucl-thhep-phPTEP(2017)·16 citations
28. 28*

    Time evolution of an unstable quantum system

    Francesco Giacosa🇩🇪

    After reviewing the description of an unstable state in the framework of Lee Hamiltonians (valid both for Quantum Mechanics (QM) and Quantum Field Theory (QFT)), we consider some theoretical aspects of non-exponential decays: the case of two decay channels, the broadening of the energy spectrum at short times, the effect of an imperfect measurement, the link to QFT, and the decay of an unstable moving particle with definite momentum. All the presented effects were not confirmed in experiments, hence are at the present stage predictions.

    ↳ quant-phhep-phActa Phys.Polon.B(2017)·8 citations
29. 29*

    Constraints on Spatially Oscillating Sub-mm Forces from the Stanford Levitated Microsphere Experiment Data

    Ioannis Antoniou🇬🇷 · Leandros Perivolaropoulos🇬🇷

    A recent analysis by one of the authors\cite{Perivolaropoulos:2016ucs} has indicated the presence of a $2\sigma$ signal of spatially oscillating new force residuals in the torsion balance data of the Washington experiment. We extend that study and analyse the data of the Stanford Optically Levitated Microsphere Experiment (SOLME) \cite{Rider:2016xaq} (kindly provided by the authors of \cite{Rider:2016xaq}) searching for sub-mm spatially oscillating new force signals. We find a statistically significant oscillating signal for a force residual of the form $F(z)=\alpha cos(\frac{2\pi }{\lambda }z+c)$ where $z$ is the distance between the macroscopic interacting masses (levitated microsphere and cantilever). The best fit parameter values are $\alpha =(1.1\pm 0.4)\times 10^{-17}N$, $\lambda =(35.2\pm 0.6)\mu m$. Monte Carlo simulation of the SOLME data under the assumption of zero force residuals has indicated that the statistical significance of this signal is at about $2\sigma$ level. Private communication with members of the SOLME group has indicated that this previously unnoticed signal is most probably due to a systematic effect (diffraction of non-Gaussian tails of the laser beam). Thus it can only be useful as an upper bound of the amplitude of new spatially oscillating forces on sub-mm scales. Assuming gravitational origin emerging from a fundamental modification of the Newtonian potential of the form $V_{eff}(r)=-G\frac{M}{r}(1+{\alpha }_O\cos (\frac{2\pi }{\lambda }r+\theta ))\equiv V_N(r)+V_{osc}(r)$, we evaluate the source integral and obtain a bound ${\alpha }_O<10^7$ for $\lambda \simeq 35\mu m$. Thus, we get no useful constraints on the modified gravity parameter ${\alpha }_O$. However, the constraints on the general phenomenological parameter $\alpha$ can be useful in constraining other fifth force models related to dark energy (chameleon oscillating potentials etc).

    ↳ gr-qcastro-ph.COhep-exhep-ph+1PRD(2017)·27 citations
30. 30*

    Quasi-normal modes of a strongly coupled non-conformal plasma and approach to criticality

    Panagiotis Betzios🇳🇱 · Umut Gürsoy🇳🇱 · Matti Järvinen🇫🇷 · Giuseppe Policastro🇫🇷

    We study fluctuations around equilibrium in a class of strongly interacting non-conformal plasmas using holographic techniques. In particular we calculate the quasi-normal mode spectrum of black hole backgrounds that approach to Chamblin-Reall plasmas in the IR. In a specific limit, related to the exact linear-dilaton background in string theory, we observe that the plasma approaches criticality and we obtain the quasi-normal spectrum analytically. We regulate the critical limit by gluing the IR geometry that corresponds to the non-conformal plasma to a part of AdS space-time in the UV. Near criticality, we find two sets of quasi-normal modes, related to the IR and UV parts of the geometry. In the critical limit, the quasi-normal modes accumulate to form a branch cut in the correlators of the energy-momentum tensor on the real axis of the complex frequency plane.

    ↳ hep-thhep-phPRD(2018)·21 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.